When it has been determined that a well should be completed, one of the conventional steps implemented is cementing a completion string in place. The cement job may extend the full length of the well bore, or partially encompass selected portions of the well bore. Moreover, it is highly desirable that the cement be delivered to the requisite locations in very rapid order so that it sets at the depths where the cement is desired, and also sets with the requisite speed to ensure a perfected bond with the formation. In conducting such a procedure, it typically will be necessary to pump at least one or two different fluids through the completion or tubing string or both and out into the annular space around the completion string. Sometimes, packers and bridge plugs will be used to isolate particular zones of the well bore. Whatever the case, typically more than one fluid will be pumped into the piping from the surface and into the well. It is very important to locate each slug of fluid at a desired location in the well.
Ordinarily, one of the fluids that will be pumped into the well is a slurry including cement. However, other fluids may be pumped into the well either before or after the cement has been delivered. In that event, it is particularly helpful to represent at the surface in graphic form the real time location of each slug. For instance, the first slug may comprise 1,500 barrels while the next slug may have a volume of 500 barrels. The two slugs will flow serially, one behind the other, and it is very important to represent their real time location so that the operator personnel at the surface can control the pumping process to ensure a proper and complete cementing job.
The flow of cement inevitably is remote from most transducers. It is relatively easy to install and locate transducers at the surface. It is an entirely different matter to locate transducers down hole, especially at the bottom of the well. The present apparatus is a device able to determine and graphically present down hole variables. These variables are important data to enable surface personnel to control the cementing job. As an example, bottom hole pressure is an important variable. It is difficult to install a bottom hole transducer for a measurement of pressure, presumably to telemeter the pressure back to the surface. This apparatus enables calculation of the bottom hole pressure and displays it on a plotter as a function of time, and will display bottom hole pressure along with other variables.
Preferably, this apparatus utilizes a plotter which provides a continuous plot of important variables. One of the variables is the bottom hole pressure as mentioned above. Another important variable is fluid density. Another variable which is helpfully displayed for the operator is pumping rate. This can be obtained from the surface by means of a flow meter installed between the pump and the well head. Equally, surface pressure is important and can be obtained at the surface.
With the foregoing in view, the apparatus of this disclosure is defined and described as a system for use with cementing equipment for delivery of cement under pressure and includes transducers for measurement of variables describing the cement flowing in the piping connected to the well head for cementing a well. The cement flow is measured including flow rate and surface pressure. Well head pressure can also be obtained. The apparatus utilizes inputs from such surface located transducers. Other set inputs are provided such as depth of well and the like. This data is stored to enable calculation and representation of down hole variables including bottom hole pressure, hydraulic horsepower, and actual hydrostatic gradients. The apparatus includes a display which is configured as a bore hole and pipe to represent thereon different slugs of serially pumped fluids so that the operator has a display suitable for representation of the annular space and the fluid slugs in the well.